1. Field of the Invention
The present invention relates to a switching assembly for performing an electrode switching operation by means of electromagnetic actuation.
2. Description of the Related Art
FIG. 24 is a general block diagram of a switching assembly which is a first conventional example employing electromagnetic repulsion such as that disclosed in xe2x80x9cShingata Kousoku Suitchi no Kaihei Dousa Tokusei (Switching Operation Characteristics of New High-Speed Switches)xe2x80x9d, Heisei 8-Nen Denki Gakkai Sangyou Ouyou Bumon Zenkoku Taikai Kouen Bangou 260 (Lecture No. 260, 1996 Institute of Electrical Engineers Industrial Applications Division All-Japan Conference), for example. FIG. 24A shows the closed state, and FIG. 24B shows the open state.
This switching assembly includes:
a switch portion 1 including a contactable fixed electrode 6 and a movable electrode 5;
a repulsion plate 2 secured to a central portion of a movable shaft 4 connected to the movable electrode 5;
an opening coil 3a for inducing current in the repulsion plate 2, the opening coil 3a being disposed on the same side of the repulsion plate 2 as the movable electrode 5 in an axial direction; and
a closing coil 3b for inducing current in the repulsion plate, the closing coil 3b being disposed on the opposite side of the repulsion plate 2 from the opening coil 3a. The opening coil 3a and the closing coil 3b are connected to a magnetic field-generating current source (not shown).
Terminals 7 connecting to a circuit are connected to the movable electrode 5 and the fixed electrode 6. Contact pressure input springs 8a and 8b for providing contact pressure between the movable electrode 5 and the fixed electrode 6 when the electrodes are closed, and an auxiliary circuit 9 working together with the opening and closing of the switch portion 1, are disposed at the opposite end of the movable shaft 4 from the movable electrode 5.
FIG. 25 is a graph showing the load characteristics of the contact pressure input springs 8a and 8b and their combined loads. In the graph, 40 are the load characteristics of the contact pressure input spring 8a, 41 are the load characteristics of the contact pressure input spring 8b, and 42 are the combined loads of the contact pressure input springs 8a and 8b. The contact pressure input springs 8a and 8b are each disposed such that a load arises in a closing direction when the combined load is in a region of deflection from the central position to the closed position, and a load is provided in an opening direction when the combined load is in a region of deflection from the central position to the open position.
Next, the opening operation of a switching device of the above construction will be explained.
In the closed state shown in FIG. 24A, a magnetic field is generated when a pulsed current is passed through the opening coil 3a. A current is thus induced in the repulsion plate 2 such that a magnetic field is generated in a direction which cancels the magnetic field generated by the opening coil 3a. By interaction between the magnetic field generated by the opening coil 3a and the magnetic field generated by the repulsion plate 2, the repulsion plate 2 is subjected to electromagnetic repulsion relative to the coil 3a. The movable shaft 4 and the movable electrode 5, which are secured to the repulsion plate, are moved in the direction of repulsion by this electromagnetic repulsion. Then, as shown in FIG. 25, as the amount of deflection of the contact pressure input springs 8a and 8b changes from the closed position to the central position, the load characteristics 42 decrease, and when the central position is exceeded, the load characteristics become load in the opening direction, and when the amount of deflection of the contact pressure input springs 8a and 8b reaches the open position, the switch 1 is held in the open state shown in FIG. 24B.
Next, the closing operation of the switching device will be explained.
In the open state shown in FIG. 24B, a magnetic field is generated when a pulsed current is passed through the closing coil 3b. A current is thus induced in the repulsion plate 2, and the repulsion plate 2 is subjected to electromagnetic repulsion relative to the closing coil 3b. The movable shaft 4 and the movable electrode 5, which are secured to the repulsion plate, are moved in the direction of repulsion by this electromagnetic repulsion. Then, as shown in FIG. 25, as the amount of deflection of the contact pressure input springs 8a and 8b changes from the open position to the central position, the load characteristics 42 increase, and when the central position is exceeded, the load characteristics become load in the closing direction, and when the amount of deflection of the contact pressure input springs 8a and 8b reaches the closed position, the switch 1 is in the closed state shown in FIG. 24A.
FIG. 26 shows the slit construction of a plunger-type electromagnet which is part of a switching device which is a second conventional example such as that disclosed in Japanese Utility Model No. SHO 58-103114, for example.
In the drawing, a movable body 101 composed of magnetic material is secured to a tip portion of a movable shaft 100. A blade spring 106 is secured to one side of the movable body 101. A fixed body 102 composed of magnetic material opposes the movable body 101 across an air gap portion 104. A coil 103 surrounded by an iron core 105 is disposed around a circumference of the fixed body 102.
FIG. 27 is a perspective of the fixed body 102 in FIG. 26, and FIG. 28 shows cross-sections of structural elements of the fixed body 102.
The fixed body 102 includes a first cylinder portion 107, a second cylinder portion 108, and a third cylinder portion 109 each formed with a slit 110 and laminated.
Next, the operation of a switching assembly of the above construction will be explained.
A magnetic field is generated when an electric current is passed through the coil 103, and this magnetic field forms a closed magnetic pathway crossing to the movable body 101 via the fixed body 102 and the air gap portion 104 and then returning to the fixed body 102 via the iron core 105. At that time, magnetic attraction arises between the movable body 101 and the fixed body 102 due to interaction between the magnetic fields generated in each. The movable shaft 100 integrated with the movable body 101 is moved in opposition to the elastic force of the blade spring 106 by this magnetic attraction. Thus, a movable electrode (not shown) connected to a tip portion of the movable shaft 100 is separated from a fixed electrode (not shown), for example, opening the contacts of the switching assembly.
When the electric current in the coil 103 is interrupted, the fixed body 102 is demagnetized and the movable shaft 100 integrated with the movable body 101 is returned to its original position by the elastic force of the blade spring 106, closing the contacts of the switching assembly.
In this switching assembly, when the magnetic field is generated, induced currents which generate electric fields in directions which obstruct the magnetic pathway arise in the movable body 101, the fixed body 102, and the iron core 105. Eddy currents which arise in the movable body 101 and the fixed body 102, in particular, obstruct swift generation of the above electromagnetic attraction, resulting in delays in the movement of the movable shaft 100. In this example, swift establishment of electromagnetic force is ensured by using a laminated construction in the fixed body 102 comprising first to third cylinder portions 107, 108, and 109 and forming slits 110 therein in order to suppress eddy currents.
In the switching assembly of the first conventional example, because the magnetic field arising in the repulsion plate 2 due to induced current is small compared to the magnetic field generated by the direct supply of electric current from the electrical circuit, the electromagnetic repulsion due to interaction between the magnetic field generated in the coil and the magnetic fields generated by induction is small, making a high energy level necessary for the closing and opening operations, and one problem has been the enlargement of the opening coil 3a and the closing coil 3b and of the power source supplying pulsed current to the opening coil 3a and the closing coil 3b. 
In the switching assembly of the second conventional example, the fixed body 102 has a laminated construction formed with slits 110, and one problem has been that the construction is complicated and preparation is difficult, raising costs. Furthermore, eddy currents are not induced in the fixed body 102 when electric current is passed through the coil 103 and the magnetic field is generated, but induced currents generating magnetic fields in directions which cancel the magnetic field generated in the coil arise in the movable body 101. Thus, because the magnetic field generated in the air gap portion 104 is small compared to the magnetic fields generated by the direct supply of electric current to the fixed body and the movable body, respectively, magnetic attraction between the movable body 101 and the fixed body 102 due to interaction with the generated magnetic field is small, delaying the operating speed, and another problem has been that it has been necessary to enlarge the coil and to enlarge the power source supplying pulsed electric current to the coil when attempting to increase the operating speed, making it necessary to increase the overall size of the assembly.
The present invention aims to solve the above problems and an object of the present invention is to provide a switching assembly enabling the energy required for the opening and closing operations to be reduced, and enabling the overall size of the assembly to be reduced by reducing the size of the driving power source.
To this end, according to the present invention, there is provided a switching assembly comprising: a switch portion comprising a fixed electrode and a movable electrode which are separable; a movable shaft moving together with the movable electrode; a movable portion having a magnetic body secured to the movable shaft and a movable coil surrounding an outer side of the magnetic body; and a fixed portion having a magnetic body slidably disposed on the movable shaft and a fixed coil surrounding an outer side of the magnetic body, the fixed portion being disposed opposite the movable portion, the fixed electrode and the movable electrode being separable by moving the movable portion and the movable shaft by electromagnetic force acting between the movable coil and the fixed coil, the electromagnetic force being generated by passage of excitation current through the movable coil and the fixed coil.
According to another aspect of the present invention, there is a switching assembly comprising: a switch portion comprising a fixed electrode and a movable electrode which are separable; a movable shaft moving together with the movable electrode; a movable portion having a movable coil and a magnetic body covering the movable coil, the movable portion being secured to the movable shaft; and a fixed portion having a fixed coil and a magnetic body covering the fixed coil, the fixed portion being disposed opposite the movable portion, the fixed electrode and the movable electrode being separable by moving the movable portion and the movable shaft by electromagnetic force acting between the movable coil and the fixed coil, the electromagnetic force being generated by passage of excitation current through the movable coil and the fixed coil.
According to still another aspect of the present invention, there is a switching assembly comprising: a switch portion comprising a fixed electrode and a movable electrode which are separable; a movable shaft moving together with the movable electrode; a movable portion comprising a dielectric body secured to the movable shaft; and a first fixed portion and a second fixed portion each having a magnetic body and a fixed coil, the first fixed portion and the second fixed portion being disposed opposite the movable portion on both sides of the movable portion in an axial direction, the fixed electrode and the movable electrode being separable by moving the movable portion and the movable shaft by electromagnetic force acting between the movable portion and the first fixed portion and between the movable portion and the second fixed portion, the electromagnetic force being generated by passage of excitation current through the fixed coil of the first fixed portion and the fixed coil of said second fixed portion.
According to another aspect of the present invention, a switching assembly comprising: a switch portion comprising a fixed electrode and a movable electrode which are separable; a movable shaft moving together with the movable electrode; a movable body secured to the movable shaft; a fixed body disposed opposite the movable body, the fixed body being slidable relative to the movable shaft; and a coil for contacting and separating the fixed body and the movable body by means of electromagnetic force generated by passage of electric current, slits for suppressing eddy currents being formed in at least one opposing surface of the movable body or the fixed body.